With proliferation of fiber-optic communication, a variety of optoelectronic assemblies have been developed for transmitting and receiving optical signals. Typically, an optoelectronic assembly includes an active device, such as a diode-laser, and an optical fiber. The active device emits the optical signal, which is coupled into the optical fiber for long distance communication. Generally, the active device and the optical fiber have different spot sizes for emitting the optical signal and receiving the optical signal, respectively. Since the spot size is inversely related to numerical aperture, the active device and the optical fiber further have different numerical apertures. This mismatch in the numerical apertures of the active device and the optical fiber, results in low coupling efficiency between the active device and the optical fiber, and further leads to coupling loss of the optical signal into the optical fiber. Thus, the optoelectronic assemblies incorporate various coupling mechanisms for improving the coupling efficiency, and thereby reducing the coupling losses.
A conventional optoelectronic assembly that uses a coupling mechanism is realized by a lensed optical fiber. In such an optoelectronic assembly, the active device is attached on an aluminum nitride sub-mount assembly and the lensed optical fiber is placed on a metalized heat sink sub-mount. The lensed optical fiber includes a lens at an input face of the optical fiber, which couples the optical signal from the active device into the optical fiber, thereby reducing the coupling loss. Such lensed fibers are usually manufactured individually, and thus suffer from process variations, which is undesirable. Further, for placing the lensed fiber on the heat sink sub-mount a high precision alignment, typically in the range of 10 μm, is required. Such a high precision alignment requirement leads to an increase in the cost and time of manufacturing the optoelectronic assembly. In addition, the use of two different sub-mounts for the active device and the lensed optical fiber makes the optoelectronic assembly bulky.
Another conventional optoelectronic assembly that uses a coupling mechanism is realized by way of a two-lens system, where the first lens serves as a collimating means and the second lens serves as a focusing means. Such a coupling mechanism includes active alignment of the first and second lenses for attaining a desired collimation and focusing output. Although the coupling mechanism realized by using the two-lens system offers high coupling efficiency and does not require high precision alignment, the use of two active alignment processes makes the coupling mechanism time consuming and complex. Typically, it takes 25-30 minutes to implement one active alignment process. As the two-lens system implements two active alignment processes, the time required for manufacturing the optoelectronic assembly is significantly increased, which is disadvantageous.
In light of the foregoing, there exists a need for an optoelectronic assembly that has high coupling efficiency, requires less precision alignment, and is less bulky. Further, it would be advantageous to have an optoelectronic assembly that does not require two active alignment processes.